Ink-jet printhead and method of manufacturing the same

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 2002-33724, filed Jun. 17, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink-jet printhead and a method of manufacturing the ink-jet printhead, and more particularly, to an ink-jet printhead including a nozzle plate having an excellent hydrophobic property and an excellent adhering property, and a method of manufacturing the ink-jet printhead.

2. Description of the Related Art

In Ink-jet printheads, an electro-thermal transducer (ink jet type) generating bubbles in ink using a heat source and ejecting ink droplets by a force generated by the bubbles is mainly used.

<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view schematically illustrating a structure of a conventional ink-jet printhead, and <figref idref="DRAWINGS">FIG. 2</figref> is a cross-sectional view of the conventional ink-jet printhead shown in FIG. <b>1</b>.

As shown in <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, the conventional ink-jet printhead includes a manifold (not shown) to which ink is supplied, a substrate <b>1</b> on which a heater <b>12</b> and a passivation layer <b>11</b> protecting the heater <b>12</b> are formed, a passage plate <b>2</b> having a passage <b>22</b> and an ink chamber <b>21</b> formed on the substrate <b>1</b>, and a nozzle plate <b>3</b> which is formed on the passage plate <b>2</b> and in which an orifice <b>31</b> corresponding to the ink chamber <b>21</b> is formed.

In general, the passage plate <b>2</b> and the nozzle plate <b>3</b> are formed by a photolithography process using polyimide. In the conventional ink-jet printhead, the passage plate <b>2</b> and the nozzle plate <b>3</b> are formed of the same material, for example, the polyimide. Due to a weak adhering property of the polyimide, the nozzle plate <b>3</b> may be detached from the passage plate <b>2</b>.

In order to solve the above problem, in a conventional method of manufacturing the conventional ink-jet printhead, if the passage plate <b>2</b> and the nozzle plate <b>3</b> are different layers formed of the polyimide as described above, the passage plate <b>2</b> and the nozzle plate <b>3</b> are separately manufactured and are then attached to the substrate <b>1</b>. In this method, due to problems including a structural misalignment, the nozzle plate <b>3</b> cannot be attached to the substrate <b>1</b> in a form of a wafer and should be attached to each chip separated from the wafer, thereby creating a disadvantage in productivity.

Meanwhile, in another conventional method of manufacturing the ink-jet printhead, a mold layer used as a sacrifice layer to form a chamber and a passage, is formed of a photoresist, then a passage plate and a nozzle plate made of the polyimide are formed on the mold layer as a single layer, and the sacrifice layer is then removed, thereby forming the chamber and the passage. If the passage plate and the nozzle plate are formed using the mold layer, the polyimide cannot be baked at a temperature high enough, so that the mold layer can be protected.

The nozzle plate of the ink-jet printhead directly faces a recording sheet and possesses several factors that influence ejection of ink droplets ejected through a nozzle. Among these factors is a hydrophobic property on a surface of the nozzle plate. If the hydrophobic property is almost non-existent, that is, if the surface of the nozzle plate has a hydrophile property, some of the ink ejected through the nozzle flows out the surface of the nozzle plate, such that the surface of the nozzle plate is contaminated and a size, a direction, and a speed of the ink droplets ejected are not uniform. As described above, the nozzle plate formed of the polyimide has the hydrophile property and thus has the above-mentioned problems. In order to solve these problems caused by the hydrophile property, in general, a coating layer used to form the hydrophobic property should be additionally formed on the surface of the nozzle plate formed of the polyimide. Metal, such as plated nickel (Ni), gold (Au), palladium (Pd), or tantalum (Ta), or a perfluoronated alkane, and silane compound having a high hydrophobic property, such as fluoronated carbon (FC), F-silane, or diamond like carbon (DLC), are used for the coating layer. The hydrophobic coating layer may be formed using a liquid method, such as spray coating or spin coating, and is deposited using a dry method, such as plasma enhanced chemical vapor deposition (PECVD) or sputtering. As a result, the coating layer used to form the hydrophobic property increases manufacturing costs.

SUMMARY OF THE INVENTION

The present invention provides a monolithic ink-jet printhead including a nozzle plate having an excellent hydrophobic property and an improved adhering property with a passage plate.

The present invention further provides a method of manufacturing a monolithic ink-jet printhead in which a nozzle plate and a passage plate are formed on a substrate at a wafer level.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

According to the above and/or other aspects of the present invention, an ink-jet printhead includes a substrate on which at least one heater and a passivation layer protecting the at least one heater are formed, a passage plate formed on the substrate to provide a chamber corresponding to the at least one heater, and a nozzle plate in which an orifice corresponding to the chamber is formed. The passage plate is formed of photoresist, and the nozzle plate is formed of a silicon-family material at a temperature limited by characteristics of the passage plate.

According to another aspect of the invention, the passage plate is formed of polyimide, and the nozzle plate is formed of one material selected from SiN, SiO₂, and SiON. According to another aspect of the invention, the nozzle plate is formed through plasma enhanced chemical vapor deposition (PECVD).

It is possible that the nozzle plate includes a first nozzle plate opposite to the passage plate and a second nozzle plate formed on the first nozzle plate, and the nozzle plate further includes a first orifice formed in the first nozzle plate and a second orifice formed in the second nozzle plate. According to another aspect of the invention, the first orifice has a diameter greater than the second orifice.

According to the above and/or other aspects of the present invention, a method of manufacturing the ink-jet printhead includes preparing a substrate on which a heater and a passivation layer protecting the heater are formed, forming a passage plate on which an ink chamber corresponding to the heater and a passage connected to the ink chamber are provided using a first photoresist, filling the ink chamber and the passage with a second photoresist, forming a nozzle plate on the passage plate using a silicon-family low-temperature deposition material, forming an orifice corresponding to the chamber in the nozzle plate, and removing the second photoresist from the chamber through wet etching.

According to another aspect of the invention, the first photoresist is formed of polyimide, and the nozzle plate is formed of SiO₂, SiN, or SiON.

It is possible that the filling of the ink chamber and the passage with the second photoresist includes coating the second photoresist on an entire surface of the passage plate, and etching back the coated second photoresist so that a portion of the second photoresist corresponding to only the ink chamber remains.

It is also possible that the forming of the nozzle plate on the passage plate includes depositing the nozzle plate formed of SiO₂, SiN, or SiON on the passage plate using plasma enhanced chemical vapor deposition (PECVD).

It is also possible preferable that between operations of forming the nozzle plate on the passage plate and forming the orifice, the first photoresist existing in the chamber is ashed using high-temperature heating, and a residue of the first photoresist is then stripped out from the chamber using a wet etchant.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which:

<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view schematically illustrating a structure of a conventional ink-jet printhead;

<figref idref="DRAWINGS">FIG. 2</figref> is a cross-sectional view of the conventional ink-jet printhead of <figref idref="DRAWINGS">FIG. 1</figref>;

<figref idref="DRAWINGS">FIG. 3</figref> is a cross-sectional view schematically illustrating an ink-jet printhead according to an embodiment of the present invention;

<figref idref="DRAWINGS">FIG. 4</figref> is a cross-sectional view schematically illustrating another ink-jet printhead according to another embodiment of the present invention;

<figref idref="DRAWINGS">FIGS. 5A through 5F</figref> illustrate a method of manufacturing the ink-jet printhead shown in <figref idref="DRAWINGS">FIG. 3</figref>; and

<figref idref="DRAWINGS">FIGS. 6A through 6H</figref> illustrate a method of manufacturing the ink-jet printhead shown in FIG. <b>4</b>.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described in order to explain the present invention by referring to the figures.

<figref idref="DRAWINGS">FIG. 3</figref> is a cross-sectional view schematically illustrating an ink-jet printhead according to an embodiment of the present invention. A heater <b>102</b> is formed on a surface of a silicon (Si) substrate <b>100</b>, and a passivation layer <b>101</b> is formed on the substrate <b>100</b>. The heater <b>102</b> is an electric heating apparatus and is connected to a conductor and pads provided on the substrate <b>100</b>. In <figref idref="DRAWINGS">FIG. 3</figref>, the conductor and pads have not been shown. A passage plate <b>200</b> formed of a photoresist, such as polyimide, is placed on the passivation layer <b>101</b>. The passage plate <b>200</b> provides an ink chamber <b>210</b> placed above the heater <b>102</b> and an ink supply passage (not shown) supplying ink to the ink chamber <b>210</b>. A nozzle plate <b>300</b> formed of a material different from the passage plate <b>200</b> is placed on the passage plate <b>200</b>. The nozzle plate <b>300</b> is formed of a silicon-family material, for example, SiO₂, SiN, SiON, or the like, having a high adhering property to the photoresist, such as the polyimide. An orifice <b>310</b>, which corresponds to the ink chamber <b>210</b> and through which ink droplets are ejected, is formed in the nozzle plate <b>300</b>.

In the above structure, the passage plate <b>200</b> is formed of the photoresist, e.g., the polyimide. It is known that the polyimide does not have a good hydrophobic property nor a good adhering property. However, the passivation layer <b>101</b> on the substrate <b>100</b> and the nozzle plate <b>300</b> on the passage plate <b>200</b> are formed of a material selected from the silicon-family material, such as SiO₂, SiN, SiON, or the like, having a low deposition temperature and good adhering properties to firmly attach the passage plate <b>200</b> and the nozzle plate <b>300</b> to the substrate <b>100</b>. The material for the nozzle plate <b>300</b> can be deposited on the passage plate <b>300</b> at a temperature limited by characteristics of the passage plate <b>200</b>. For example, the polyimide can be deposited at a temperature lower than 350° C. Thus, the nozzle plate <b>300</b> can be formed directly over a polyimide layer, and the passage plate <b>200</b> and the nozzle plate <b>300</b> can be formed on the substrate <b>100</b> at a wafer level, that is, a plurality of printheads are formed on a wafer by forming a plurality of passage plates <b>200</b> and nozzle plates <b>300</b> on the wafer.

<figref idref="DRAWINGS">FIG. 4</figref> is a cross-sectional view schematically illustrating another ink-jet printhead according to another embodiment of the present invention.

Referring to <figref idref="DRAWINGS">FIG. 4</figref>, the nozzle plate <b>300</b> includes first and second nozzle plates <b>301</b> and <b>302</b> in which first and second orifices <b>311</b> and <b>312</b> having different diameters are formed. It is possible that the first and second nozzle plates <b>302</b> are formed of the same material, in particular, the silicon-family material as described above. Due to the first and second orifices <b>311</b> and <b>312</b> formed in the first and second nozzle plates <b>301</b> and <b>302</b> respectively, a diameter of an orifice <b>310</b> of the nozzle plate <b>300</b> having the first and second nozzle plates <b>301</b> and <b>302</b> becomes narrower in a direction in which droplets fall or are ejected, to increase a directional accuracy of the droplets.

Hereinafter, a method of manufacturing the ink-jet printhead shown in <figref idref="DRAWINGS">FIG. 3</figref> will be described.

In the following descriptions of the method of manufacturing the ink-jet printhead shown in <figref idref="DRAWINGS">FIG. 3</figref>, well-known techniques, in particular, techniques used to manufacture a conventional ink-jet printhead, will not be described in detail.

<figref idref="DRAWINGS">FIGS. 5A through 5F</figref> illustrate the method of manufacturing the ink-jet printhead shown in FIG. <b>3</b>.

The substrate <b>100</b> in a silicon wafer state on which the heater <b>102</b> and lower layers including an SiN passivation layer <b>101</b> protecting the heater <b>102</b> are formed, is prepared as shown in FIG. <b>5</b>A. The above operation is performed at the wafer level and is accompanied by an operation of forming a material for the heater <b>102</b>, a patterning operation, and another operation of depositing the passivation layer <b>101</b> on the substrate <b>100</b>.

The photoresist, for example, the polyimide, is coated on an entire surface of the substrate <b>100</b> to a thickness of several tens of microns, for example, 30 microns, and is then patterned using photolithography, thereby forming an ink chamber <b>210</b> and an ink passage (not shown) connected to the ink chamber <b>210</b> as shown in FIG. <b>5</b>B. After the above patterning operation is performed, an operation of forming the passage plate <b>200</b> is completed using the polyimide in a hard baking process.

A mold layer <b>211</b> is formed of the photoresist in the ink chamber <b>210</b> as a sacrifice layer, as shown in FIG. <b>5</b>C. Here, after the photoresist is coated on an entire surface of the passage plate <b>200</b> and a portion of the substrate <b>100</b>, a photolithography process of performing an etch-back process in which the photoresist corresponding to only the ink chamber <b>210</b> remains may be applied to the photoresist formed on the passage plate <b>200</b> by using either an entire surface-etch process or a partial-exposure and etch process.

The nozzle plate <b>300</b> is formed on the passage plate <b>200</b> and the mold layer <b>211</b> by depositing an SiO₂, SiN, or SiON layer using a low temperature deposition method at a temperature under 400° C., for example, using plasma enhanced chemical vapor deposition (PECVD) as shown in FIG. <b>5</b>D.

The orifice <b>310</b> corresponding to the ink chamber <b>210</b> is formed in the nozzle plate <b>300</b> as shown in FIG. <b>5</b>E. The orifice <b>310</b> is formed when an operation of forming a mask using the photoresist and the patterning operation are performed through wet and dry etching.

The mold layer <b>211</b> is removed from the ink chamber <b>210</b> as shown in FIG. <b>5</b>F. Using ashing and striping processes performed during a process of removing the mask used for forming the orifice <b>310</b> after formation of the orifice <b>310</b>, the mold layer <b>211</b> can also be removed from the ink chamber <b>210</b>. A residue in the mold layer <b>211</b> and the photoresist remaining on another passage can be removed using a wet etchant after an operation of forming an ink feed hole on a rear surface of the substrate <b>100</b>.

<figref idref="DRAWINGS">FIGS. 6A through 6H</figref> illustrate another method of manufacturing the ink-jet printhead shown in FIG. <b>4</b>. The identical operations of the method shown in <figref idref="DRAWINGS">FIGS. 5A through 5F</figref> may be used in the method of <figref idref="DRAWINGS">FIGS. 6A through 6H</figref>.

The substrate <b>100</b> in the silicon wafer state, on which the heater <b>102</b> and the lower layers including the SiN passivation layer <b>101</b> protecting the heater <b>102</b> are formed, is prepared as shown in FIG. <b>6</b>A. The above operation is performed at the wafer level and is accompanied by an operation of forming the material for the heater <b>102</b>, the patterning operation, and another operation of depositing the passivation layer <b>101</b> on the substrate <b>100</b>.

The photoresist, for example, the polyimide, is coated on the entire surface of the substrate <b>100</b> to a thickness of several tens of microns, for example, 30 microns, and is then patterned using the photolithography, thereby forming the ink chamber <b>210</b> and the ink passage (not shown) connected to the ink chamber <b>210</b> as shown in FIG. <b>6</b>B. After the above patterning operation, the passage plate <b>200</b> is completed using the polyimide in the hard baking process.

The mold layer <b>211</b> is formed of the photoresist in the ink chamber <b>210</b> as the sacrifice layer, as shown in FIG. <b>6</b>C. Here, after the photoresist is coated on the entire surface of the passage plate <b>200</b> and a portion of the substrate <b>100</b>, the photolithography process of performing the etch-back process in which the photoresist corresponding to only the ink chamber <b>210</b> remains may be applied to the photoresist formed on the passage plate <b>200</b> by using either the entire surface-etch process or a partial-exposure process and an etch process.

The nozzle plate <b>300</b> is formed on the passage plate <b>200</b> and the mold layer <b>211</b> by sequentially depositing an SiO₂, SiN, or SiON layer, that is, two layers <b>301</b> and <b>302</b>, using a low temperature deposition method at a temperature under 400° C., for example, using the plasma enhanced chemical vapor deposition (PECVD) as shown in FIG. <b>6</b>D. Here, a lower first nozzle plate <b>301</b> is formed of SiO₂, and an upper second nozzle plate <b>302</b> is formed of SiN having a wet etch rate higher than SiO₂.

A photoresist mask <b>401</b> is formed on the nozzle plate <b>300</b> including the first nozzle plate <b>301</b> and the second nozzle plate <b>302</b>, and the orifice <b>310</b> corresponding to the ink chamber <b>210</b> is then formed in the nozzle plate <b>300</b> using the photoresist mask <b>401</b> as shown in FIG. <b>6</b>E. The orifice <b>310</b> includes the first orifice <b>311</b> formed in the first nozzle plate <b>301</b> and the second orifice <b>302</b> formed in the second nozzle plate <b>312</b>. The first and second orifices <b>311</b> and <b>312</b> of the orifice <b>310</b> have the same diameters by etching using dry etching.

The mask <b>401</b> is removed using the ashing and stripping processes as shown in FIG. <b>6</b>F. In this case, the mold layer <b>211</b> is removed together with the mask <b>401</b> from the ink chamber <b>210</b>, and only a partial residual remains in the mold layer <b>211</b>.

The first orifice <b>311</b> in the first nozzle plate <b>301</b> is etched by supplying HF, BOE, and LAL to the orifice <b>310</b>, thereby increasing the diameter of the first orifice <b>311</b> as shown in FIG. <b>6</b>G. The residual in the mold layer <b>211</b> and the photoresist existing on another passage can be removed using the wet etchant after an operation of forming an ink feed hole on the rear surface of the substrate <b>100</b>, thereby completing a desired ink-jet printhead as shown in FIG. <b>4</b>.

As described above, in the ink-jet printhead and the method of manufacturing the ink-jet printhead according to the present invention, even though a passage plate and a nozzle plate are separately formed, the passage plate and the nozzle plate can be well attached to a substrate such that the passage plate and the nozzle plate are continuously formed at a wafer level. Since it is possible that the passage plate and the nozzle plate are continuously formed on a wafer at the wafer level, yield of the ink-jet printhead is improved, and manufacturing costs are reduced. In addition, the nozzle plate is formed of a silicon-family material, such that the nozzle plate has a hydrophobic property. Thus, the nozzle plate is prevented from becoming soaked with the ink. In other words, the nozzle plate is prevented from being contaminated by the ink. Further, since the nozzle plate itself has the hydrophobic property, an additional coating layer is not needed.

While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.